1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a light emitting diode (LED)-based optical system and a method of compensating for aging thereof. More particularly, the present invention relates to an LED-based optical system and a method of compensating for aging thereof, which may ensure a uniform picture quality by compensating for the non-uniformity of outputs of LED blocks occurring due to the differences in aging speed among the respective LED blocks.
2. Description of the Related Art
Recently, LEDs have been used for the purpose of illumination, and the development of LEDs for use as a backlight is in full swing. LEDs generate light of a relatively narrow spectrum that is influenced by a band gap of the semiconductor material used. Specifically, through the combination of R (red), G (green), and B (blue) LEDs, a mixed light and a white light may be generated. During the generation of the mixed light and the white light, a shade difference induced by varying the mixing rates of respective color LEDs appears as a color variation to produce the mixed colors. Accordingly, in the case of producing a lighting fixture using LEDs, the mixing rates among the respective color LEDs should be kept constant.
The optical characteristics of an LED may permanently change according to its own characteristics and the surrounding environment, and this permanent change in optical characteristics is called aging or degeneration. The aging speed differs according to the characteristics of the respective LED, and is heightened when the temperature surrounding the LED becomes high or when a high power is supplied.
On the other hand, LEDs installed in a large-area display panel are grouped into LED blocks, and in one LED block, LEDs having similar output characteristics are arranged. Here, the output characteristics refer to the amounts of energy outputted from LEDs when the same amount of current is supplied thereto. By arranging LEDs having the similar output characteristics in one LED block, it is possible to control LED blocks in accordance with the output characteristics of the LEDs. Accordingly, the output differences which may occur among the respective LED blocks due to the differences in output characteristics of the LEDs may be prevented.
However, in the case of a large-area display panel, differences in temperature among the respective LED blocks may occur due to their respective positions, and the aging speed of an LED block arranged in a high-temperature area may be as much as twice as high than that of an LED block arranged in a low-temperature area.
If the differences in aging speed occur among the LED blocks as described above, the colors outputted from the respective LED blocks may differ although they are controlled to output the same color. Due to the color deviation among the LED blocks, partial color non-uniformity may occur in the whole display panel to decrease the picture quality and lead to a user's dissatisfaction.
Accordingly, a need exists for a compensation method capable of minimizing the non-uniformity of colors among the respective LED blocks occurring due to the differences in aging speed among the respective LED blocks.